The present invention relates generally to a process of coal liquefaction and more particularly to an apparatus for effective distribution of hydrogen into a coal paste in the liquefaction reactor.
Coal can be converted to valuable products by subjecting coal to solvent extraction, with the addition of hydrogen, to produce a mixture of coal extract and undissolved coal residue, the residue including undissolved extractable carbonaceous matter, fusain and mineral matter or ash. The undissolved coal residue is separated from the coal extract and valuable products are recovered from the coal extract.
In the process, ground or pulverized coal, generally bituminous, sub-bituminous or lignite, is introduced into a coal solvation and slurrying zone along with a coal liquefaction solvent. The solvent is added to the pulverized material in an amount sufficient to effect the subsequently desired liquefaction and produces a coal paste. The paste is introduced into a coal liquefaction zone wherein, with application of heat and pressure the coal is converted to liquid products. The process in the liquefaction zone, known in the art, may be catalytic or non-catalytic and may be effected in the presence or absence of added hydrogen, but preferably in the presence of added hydrogen. This hydrogenation, as known in the art, increases the recovery of coal products and also reduces the sulfur and nitrogen content of the recovered liquid coal product. The liquefaction is preferably effected in an upflow ebullated bed e.g., as described in U.S. Pat. No. 2,987,465.
The liquefaction or digestion of the coal in the pasting solvent is effected at temperatures and pressures, which generally range from about 700.degree. F. to about 1000.degree. F. and with a pressure up to 10,000 psia. The reaction conditions for effecting liquefaction of the coal are well known in the art and form no part of the present invention.
The insoluble material in the liquefaction zone is then separated from the coal extract to provide a coal extract essentially free of insoluble matter.
There is a need for new and improved techniques in such a coal liquefaction process in order to provide an economic process for producing clean fuel from coal. A difficulty occurring in present systems relates to the proper introduction of hydrogen into a bed of coal paste. Uniform distribution of hydrogen within the paste, maintenance of proper quantitative ratios of materials, and adequate mixture of hydrogen and paste present problems which affect the overall operational efficiency of the apparatus and process.